So it seems the tangential water input seems the way to go with these jets, but in my design this is causing a problem. I am making the main tube from acrylic, which is quite brittle, and drilling a big hole in the side of an acrylic cylinder is a great way to compromise the strength of it. I also find a lot of the tangent water inputs to be fairly messy with glue and primer everywhere, probably prone to leaks and vulnerable to being whacked and damaged.

The base on my jet is 20mm thick PTFE, Nylon or similar, and im going to CNC cut it, so I can be quite precise with the shapes. I am wondering if a tube coming through the bottom plate with a 90 degree elbow that then points inside along the edge of the tube, creating a tangential flow. This also gives us the opportunity to swivel it round and experiment to see if any other angles perform better, and we could put all sorts of accessories on the end of the pipe to direct the flow round inside the first chamber.

I have done a basic rendering to show what I mean. What do we think, good idea or not? I think it would do the same job and cut out loads of the problems of building an acrylic tube with a normal tangential water input...

That sounds like a great idea. Simple to machine, and easy to assemble. I suppose the only drawback to the design is as the water flows around the bottom it will be obstructed by the input as it flow around. THough I don't know how important that is. I can't wait to see how it works. It's definitely worth a try.

I thought this, but theres nothing to stop us putting two inlets in to get the swirl going. Maybe an obstacle like that would do it good, has anyone ever tried putting baffles or anything in the bottom? Seems to me it would help slow the water down rather than speed it up.

Maybe rather than pointing the tube out like that we could spin it round so it crosses the centre of the tube, with another tube on it, so the outlet tube is down the middle of the chamber, with holes in it. This would distribute the pressure evenly into the first chamber... All easy to test with a system like this...